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ADS1299: ADS1299

Shimon Hayun
Prodigy 20 points
Part Number: ADS1299

Hello,

Using the ADS1299 in monopolar mode, all IN_P lines are sorted together, connected to GND and used as the reference. The IN_P lines are used as the reference for the IN_N lines, which are then connected to the analog inputs of the ADS1299.

 

At the input of each IN_N input, I have added a preamplifier. This mode of operation allows the IN_N pins to measure the voltage difference between the reference (GND) and the analog input. The preamplifier amplifies the voltage signal from the analog input before sending it to the ADS1299, resulting in a more accurate measurement.

Can you guide me on how to use the Lead Off Detection mechanism if I have a preamp before the input? The Lead Off Detection mechanism uses the IN_N pins to measure the difference in voltage between the reference (GND) and the analog input. The IN_N pins can still measure the voltage difference with a preamp before the input. However, the preamp must be set up in a special configuration so that the Lead Off Detection circuit can detect the voltage difference between the reference and the analog input. 

Your support is greatly appreciated. 

  • 0
    TI__Mastermind 19815 points

    Hi,

    What do you mean by "monopolar mode"? 

    Could you refer to datasheet and specify whether it's  Sequential(i.e. differential) montage or Referential(Single End) montage?

    ------------------------------------------------

    Regarding to the Lead off detection with Pre-amp-

    May I first ask, why do you need a PreAmp?

    -------------------------

    Typically, we don't support the lead off detection if there is PreAmp as it may disrupt the voltage or current path for the lead off detection circuit.

    What lead off detection method do you plan to use?

    a) External Pull-Up or Pull-Down Resistors
    b) Input Current Source

    or

    c) AC Lead-off detection

    ------------------------------

    Would you mind sharing portion of your schematic?  If not allowed, I can reach out to you via email.

    Thanks

  • +1 in reply to ChienChun Yang
    Prodigy 20 points

    Hi chienChun,

    Thanks for replaying back to me 


    1. The phrasing Monopolar relates to connectivity method as described in the datasheets of the ADS1299 on page 67 (See Fig below) 

    2.PreAmp was added because we use dry electrodes (Silver metal) and I understand that PreAmp increases the input impedance near the electrode (the pre amp is located very near the electrode).

    I will appreciate your review on the peramp design.

    I would like to test all three methods for LOF detection  

    email will be perfect shayon@snapchat.com

    Shimon

  • +1 in reply to Shimon Hayun
    TI__Mastermind 19815 points

    Hi,

    I will reach out to you via email.

    Thanks

  • +1 in reply to ChienChun Yang
    TI__Mastermind 19815 points

    Let's continue using email for future discussion.

    Closing this ticket now.

    Thanks